Modified alumina coating and its preparation method and application

Abstract

The application discloses a modified alumina coating and a preparation method and application thereof, and belongs to the technical field of coatings.The modified alumina coating comprises the following components: modified alumina and water-based polyurethane emulsion; the preparation method of the modified alumina comprises the following steps: mixing alumina, L-cysteine and carboxymethyl chitosan to obtain the modified alumina; the weight ratio of the alumina, the L-cysteine and the carboxymethyl chitosan is 5:(1-5):(1-8); the raw materials of the water-based polyurethane emulsion comprise the following components in the following proportions by weight: 100 parts of toluene-2,4-diisocyanate, 120-180 parts of polypropylene glycol, 15-60 parts of citric acid, 0.2-5 parts of a catalyst, 10-50 parts of triethylamine and 80-300 parts of water.The modified alumina can not only improve the antibacterial property of the alumina, but also improve the compatibility between the alumina and the water-based polyurethane emulsion, so that the antibacterial and corrosion-resistant properties of the modified alumina coating are improved.

Description

Technical Field

[0001] This invention relates to the field of coating technology, and more specifically, to a modified alumina coating, its preparation method, and its application. Background Technology

[0002] If the surfaces of various objects that humans come into daily contact with are suitable for bacterial survival, bacteria will often proliferate rapidly. Furthermore, when people's hands directly and frequently touch these surfaces, bacteria carried on their skin can be transferred to the surfaces, further promoting the spread of bacteria. Therefore, using disinfectants and creating self-disinfecting surfaces on various objects are considered the most effective methods for solving bacterial infection problems.

[0003] Applying or spraying antibacterial coatings to the surfaces of various items is a method of creating self-disinfecting surfaces. This effectively reduces bacterial growth on surfaces, lowering the risk of infection through contact transmission. It can also provide a non-antibiotic solution, helping to slow the development of bacterial resistance. Currently, this method of applying or spraying antibacterial coatings to the surfaces of various items is widely used in home decoration, automotive interiors, marine corrosion protection, and industrial corrosion protection.

[0004] Antibacterial coatings refer to coatings containing antibacterial agents. Compared with silver ion antibacterial agents, alumina, as an antibacterial agent, has antioxidant and heat-resistant properties, and its lower cost makes it more suitable for widespread application. However, when alumina is added to coatings as an antibacterial agent, the compatibility between alumina and the coating is poor, leading to a decrease in the antibacterial and corrosion-resistant properties of the coating.

[0005] Therefore, developing a modified alumina coating with high antibacterial and corrosion-resistant properties is of great significance. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide a modified alumina coating with high antibacterial and corrosion-resistant properties, its preparation method, and its application.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] In a first aspect, the present invention provides a modified alumina coating comprising the following components:

[0009] Modified alumina and waterborne polyurethane emulsion;

[0010] The method for preparing the modified alumina includes: mixing alumina, L-cysteine ​​and carboxymethyl chitosan to obtain the modified alumina; the weight ratio of the alumina, L-cysteine ​​and carboxymethyl chitosan is 5:(1-5):(1-8).

[0011] The raw materials of the aqueous polyurethane emulsion include the following components in parts by weight:

[0012] 100 parts toluene-2,4-diisocyanate (TDI), 120-180 parts polypropylene glycol, 15-60 parts citric acid, 0.2-5 parts catalyst, 10-50 parts triethylamine, and 80-300 parts water.

[0013] The modified alumina coating of the present invention has high antibacterial and corrosion-resistant properties.

[0014] Specifically, this invention modifies alumina by controlling the weight ratio of alumina, L-cysteine, and carboxymethyl chitosan. This not only improves the antibacterial properties of alumina but also enhances the compatibility between alumina and waterborne polyurethane emulsions. This allows the modified alumina to be stably and uniformly dispersed in the modified alumina coating, thereby achieving the goal of improving the antibacterial and corrosion-resistant properties of the modified alumina coating.

[0015] In addition, the waterborne polyurethane emulsion synthesized by controlling the amount of toluene-2,4-diisocyanate (TDI), polypropylene glycol and citric acid has good compatibility with modified alumina, which can improve the dispersion and uniformity of modified alumina in modified alumina coatings, and help improve the antibacterial and corrosion-resistant properties of modified alumina coatings.

[0016] Preferably, the weight ratio of alumina, L-cysteine, and carboxymethyl chitosan is 5:(2-4):(3-6).

[0017] More preferably, the weight ratio of alumina, L-cysteine, and carboxymethyl chitosan is 5:3:5.

[0018] Preferably, the average particle size of the alumina is 30-800 nm.

[0019] More preferably, the average particle size of the alumina is 100-500 nm.

[0020] More preferably, the alumina has an average particle size of 250 nm.

[0021] Preferably, the average molecular weight of the polypropylene glycol is 400-4000.

[0022] More preferably, the average molecular weight of the polypropylene glycol is 1000-3000.

[0023] More preferably, the average molecular weight of the polypropylene glycol is 2000.

[0024] Preferably, the polypropylene glycol is present in 140-160 parts by weight.

[0025] More preferably, the polypropylene glycol is 150 parts by weight.

[0026] Preferably, the citric acid is present in 30-50 parts by weight.

[0027] More preferably, the citric acid is present in 40 parts by weight.

[0028] Preferably, the weight ratio of the modified alumina to the waterborne polyurethane emulsion is (5-30):100.

[0029] More preferably, the weight ratio of the modified alumina to the waterborne polyurethane emulsion is (10-20):100.

[0030] More preferably, the weight ratio of the modified alumina to the waterborne polyurethane emulsion is 15:100.

[0031] Preferably, the modified alumina coating further includes additives.

[0032] More preferably, the additive is at least one of defoamer, wetting agent, leveling agent, and filler.

[0033] Commonly used defoamers, wetting agents, and leveling agents in this field can all be used in this invention.

[0034] More preferably, the weight ratio of the additive to the aqueous polyurethane emulsion is (0.1-20):100.

[0035] Preferably, the method for preparing the modified alumina includes: adding alumina, L-cysteine ​​and carboxymethyl chitosan to a solvent, mixing them, and drying them to obtain the modified alumina;

[0036] More preferably, the solvent is water.

[0037] More preferably, the drying temperature is 50-95°C.

[0038] Preferably, the method for preparing the aqueous polyurethane emulsion includes the following steps:

[0039] S1. Mix toluene-2,4-diisocyanate (TDI), polypropylene glycol and catalyst, and carry out a prepolymerization reaction to obtain a prepolymer;

[0040] S2. Citric acid and triethylamine are added to the prepolymer to react and obtain the intermediate;

[0041] S3. Add water to the intermediate to carry out an emulsification reaction, and the waterborne polyurethane emulsion is obtained.

[0042] More preferably, in step S1, the temperature of the prepolymerization reaction is 70-85°C.

[0043] More preferably, in step S1, the prepolymerization reaction takes 0.5-24 hours.

[0044] More preferably, in step S1, the prepolymerization reaction is carried out in an inert gas atmosphere.

[0045] More preferably, the inert gas is at least one of nitrogen and argon.

[0046] More preferably, in step S2, the reaction temperature is 50-80°C.

[0047] More preferably, in step S2, the reaction time is 0.5-6 hours.

[0048] Preferably, the catalyst is at least one of zinc octanoate, dibutyltin dilaurate, and stannous octanoate.

[0049] Secondly, the present invention provides a method for preparing a modified alumina coating, comprising:

[0050] The modified alumina coating is obtained by mixing the components.

[0051] Thirdly, the present invention provides an application of modified alumina coating in antibacterial applications.

[0052] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0053] The modified alumina coating of the present invention has high antibacterial and corrosion-resistant properties.

[0054] Specifically, this invention modifies alumina by controlling the weight ratio of alumina, L-cysteine, and carboxymethyl chitosan. This not only improves the antibacterial properties of alumina but also enhances the compatibility between alumina and waterborne polyurethane emulsions. This allows the modified alumina to be stably and uniformly dispersed in the modified alumina coating, thereby achieving the goal of improving the antibacterial and corrosion-resistant properties of the modified alumina coating.

[0055] In addition, the waterborne polyurethane emulsion synthesized by controlling the amount of toluene-2,4-diisocyanate (TDI), polypropylene glycol and citric acid has good compatibility with modified alumina, which can improve the dispersion and uniformity of modified alumina in modified alumina coatings, and help improve the antibacterial and corrosion-resistant properties of modified alumina coatings. Attached Figure Description

[0056] Figure 1 Figure A shows the modified alumina coating of Example 1 and Comparative Example 1 coated on a tinplate surface, and Figure B shows the modified alumina coating of Comparative Example 1 coated on a tinplate surface. Detailed Implementation

[0057] To better illustrate the purpose, technical solution, and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments.

[0058] The experimental methods in the following examples and comparative examples, where specific conditions are not specified, are generally performed under conventional conditions in the art or as recommended by the manufacturer; the raw materials and reagents used, unless otherwise specified, are all commercially available from the conventional market.

[0059] The reagents used in the various embodiments and comparative examples of this invention are as follows:

[0060] Alumina-1, with an average particle size of 250 nm, Brofos-AlO3-250, Bohuas Nanotechnology (Ningbo) Co., Ltd.;

[0061] Alumina-2, with an average particle size of 500nm, Brofos-AlO3-500, Bohuas Nanotechnology (Ningbo) Co., Ltd.;

[0062] Alumina-3, with an average particle size of 100nm, Brofos-AlO3-100, Bohuas Nanotechnology (Ningbo) Co., Ltd.;

[0063] Alumina-4, with an average particle size of 800nm, Brofos-AlO3-800, Bohuas Nanotechnology (Ningbo) Co., Ltd.;

[0064] Alumina-5, with an average particle size of 30nm, Brofos-AlO3-30, Bohuas Nanotechnology (Ningbo) Co., Ltd.;

[0065] L-cysteine, L804954, Shanghai Maclean's;

[0066] Carboxymethyl chitosan, C804727, Shanghai Maclean;

[0067] Polypropylene glycol-1, average molecular weight 2000, P103208, Shanghai Aladdin;

[0068] Polypropylene glycol-2, average molecular weight 3000, P103211, Shanghai Aladdin;

[0069] Polypropylene glycol-3, average molecular weight 1000, P103210, Shanghai Aladdin;

[0070] Polypropylene glycol-4, average molecular weight 4000, P103212, Shanghai Aladdin;

[0071] Polypropylene glycol-5, average molecular weight 400, P103209, Shanghai Aladdin;

[0072] Catalyst, dibutyltin dilaurate, commercially available;

[0073] Leveling agent, BYK-333, BYK;

[0074] Defoamer, BYK-028, BYK.

[0075] Example 1

[0076] This embodiment provides a modified alumina coating, comprising the following components in parts by weight:

[0077] 100 parts modified alumina, 15 parts waterborne polyurethane emulsion, 3 parts leveling agent, 2 parts defoamer;

[0078] The method for preparing the modified alumina includes: adding alumina-1 (average particle size of 250 nm), L-cysteine ​​and carboxymethyl chitosan to water, stirring to mix, and drying at 65°C to obtain the modified alumina.

[0079] The weight ratio of alumina-1, L-cysteine, and carboxymethyl chitosan is 5:3:5;

[0080] The raw materials of the aqueous polyurethane emulsion include the following components in parts by weight:

[0081] 100 parts toluene-2,4-diisocyanate (TDI), 150 parts polypropylene glycol-1 (average molecular weight 2000), 40 parts citric acid, 3 parts catalyst, 30 parts triethylamine, 150 parts water;

[0082] The method for preparing the aqueous polyurethane emulsion includes the following steps:

[0083] S1. Mix toluene-2,4-diisocyanate (TDI), polypropylene glycol-1 and catalyst, and heat to 80°C for 4 hours under a nitrogen atmosphere to obtain a prepolymer;

[0084] S2. Citric acid and triethylamine are added to the prepolymer, and the reaction is carried out at 80°C for 3 hours to obtain the intermediate;

[0085] S3. Add water to the intermediate and perform an emulsification reaction by ultrasound to obtain an aqueous polyurethane emulsion.

[0086] The preparation method of the above-mentioned modified alumina coating includes:

[0087] The modified alumina coating is obtained by mixing the components.

[0088] Examples 2-9 and Comparative Examples 1-4

[0089] Examples 2-9 and Comparative Examples 1-4 provide different modified alumina coatings. The difference between them and Example 1 lies in the weight ratio of alumina-1, L-cysteine, and carboxymethyl chitosan. All other aspects are the same as in Example 1, as shown in the table below:

[0090] Table 1. Weight ratio of alumina-1, L-cysteine, and carboxymethyl chitosan in Examples 1-9 and Comparative Examples 1-4

[0091]

[0092] Examples 10-13

[0093] Examples 10-13 provide different modified alumina coatings, which differ from Example 1 in that they use different types of alumina; otherwise, they are the same as Example 1, as shown in the table below:

[0094] Table 2. Types of Alumina in Examples 1 and 10-13

[0095] Types of aluminum oxide Average particle size of alumina / nm Example 1 Alumina-1 250 Example 10 Alumina-2 500 Example 11 Alumina-3 100 Example 12 Alumina-4 800 Example 13 Alumina-5 30

[0096] Examples 14-17

[0097] Examples 14-17 provide different modified alumina coatings, which differ from Example 1 in the type of polypropylene glycol used; otherwise, they are identical to Example 1, as detailed in the table below:

[0098] Table 3. Types of polypropylene glycol in Examples 1, 14-17 and Comparative Example 5.

[0099] Types of polypropylene glycol Average molecular weight of polypropylene glycol Example 1 Polypropylene Glycol-1 2000 Example 14 Polypropylene Glycol-2 3000 Example 15 Polypropylene Glycol-3 1000 Example 16 Polypropylene Glycol-4 4000 Example 17 Polypropylene Glycol-5 400

[0100] Examples 18-21 and Comparative Examples 5-6

[0101] Examples 18-21 and Comparative Examples 5-6 provide different modified alumina coatings, differing from Example 1 in the weight percentage of polypropylene glycol-1; otherwise, they are identical to Example 1, as detailed in the table below:

[0102] Table 4. Parts by weight of polypropylene glycol-1 in Examples 1, 18-21 and Comparative Examples 5-6

[0103] Parts by weight of polypropylene glycol-1 Example 1 150 Example 18 160 Example 19 140 Example 20 180 Example 21 120 Comparative Example 5 200 Comparative Example 6 0

[0104] Examples 22-25 and Comparative Examples 7-8

[0105] Examples 22-25 and Comparative Examples 7-8 provide different modified alumina coatings, differing from Example 1 in the weight percentage of citric acid; otherwise, they are identical to Example 1, as detailed in the table below:

[0106] Table 5. Parts by weight of citric acid in Examples 1, 22-25 and Comparative Examples 7-8

[0107] citric acid weight parts / serving Example 1 40 Example 22 50 Example 23 30 Example 24 60 Example 25 15 Comparative Example 7 80 Comparative Example 8 0

[0108] Examples 26-29 and Comparative Example 9

[0109] Examples 26-29 and Comparative Example 9 provide different modified alumina coatings, differing from Example 1 in the weight ratio of modified alumina and waterborne polyurethane emulsion. All other aspects are the same as in Example 1, as detailed in the table below:

[0110] Table 6 shows the weight ratios of modified alumina and waterborne polyurethane emulsions in Examples 1, 26-29, and Comparative Example 9.

[0111]

[0112] Example 30

[0113] This embodiment provides a modified alumina coating, comprising the following components in parts by weight:

[0114] 100 parts modified alumina, 15 parts waterborne polyurethane emulsion, 0 parts leveling agent, 0 parts defoamer;

[0115] The method for preparing the modified alumina includes: adding alumina-1 (average particle size of 250 nm), L-cysteine ​​and carboxymethyl chitosan to water, stirring to mix, and drying at 65°C to obtain the modified alumina.

[0116] The weight ratio of alumina-1, L-cysteine, and carboxymethyl chitosan is 5:3:5;

[0117] The raw materials of the aqueous polyurethane emulsion include the following components in parts by weight:

[0118] 100 parts toluene-2,4-diisocyanate (TDI), 150 parts polypropylene glycol-1 (average molecular weight 2000), 40 parts citric acid, 3 parts catalyst, 30 parts triethylamine, 150 parts water;

[0119] The method for preparing the aqueous polyurethane emulsion includes the following steps:

[0120] S1. Mix toluene-2,4-diisocyanate (TDI), polypropylene glycol-1 and catalyst, and heat to 80°C for 4 hours under a nitrogen atmosphere to obtain a prepolymer;

[0121] S2. Citric acid and triethylamine are added to the prepolymer, and the reaction is carried out at 80°C for 3 hours to obtain the intermediate;

[0122] S3. Add water to the intermediate and perform an emulsification reaction by ultrasound to obtain an aqueous polyurethane emulsion.

[0123] The preparation method of the above-mentioned modified alumina coating includes:

[0124] The modified alumina coating is obtained by mixing the components.

[0125] Example 31

[0126] This embodiment provides a modified alumina coating, comprising the following components in parts by weight:

[0127] 100 parts modified alumina, 10 parts waterborne polyurethane emulsion, 1 part leveling agent, 1 part defoamer;

[0128] The method for preparing the modified alumina includes: adding alumina-1 (average particle size of 250 nm), L-cysteine ​​and carboxymethyl chitosan to water, stirring to mix, and drying at 65°C to obtain the modified alumina.

[0129] The weight ratio of alumina-1, L-cysteine, and carboxymethyl chitosan is 5:3:5;

[0130] The raw materials of the aqueous polyurethane emulsion include the following components in parts by weight:

[0131] 100 parts toluene-2,4-diisocyanate (TDI), 140 parts polypropylene glycol-1 (average molecular weight 2000), 30 parts citric acid, 0.2 parts catalyst, 10 parts triethylamine, 80 parts water;

[0132] The method for preparing the aqueous polyurethane emulsion includes the following steps:

[0133] S1. Mix toluene-2,4-diisocyanate (TDI), polypropylene glycol-1 and catalyst, and heat to 80°C for 4 hours under a nitrogen atmosphere to obtain a prepolymer;

[0134] S2. Citric acid and triethylamine are added to the prepolymer, and the reaction is carried out at 80°C for 3 hours to obtain the intermediate;

[0135] S3. Add water to the intermediate and perform an emulsification reaction by ultrasound to obtain an aqueous polyurethane emulsion.

[0136] The preparation method of the above-mentioned modified alumina coating includes:

[0137] The modified alumina coating is obtained by mixing the components.

[0138] Example 32

[0139] This embodiment provides a modified alumina coating, comprising the following components in parts by weight:

[0140] 100 parts modified alumina, 20 parts waterborne polyurethane emulsion, 5 parts leveling agent, 5 parts defoamer;

[0141] The method for preparing the modified alumina includes: adding alumina-1 (average particle size of 250 nm), L-cysteine ​​and carboxymethyl chitosan to water, stirring to mix, and drying at 65°C to obtain the modified alumina.

[0142] The weight ratio of alumina-1, L-cysteine, and carboxymethyl chitosan is 5:3:5;

[0143] The raw materials of the aqueous polyurethane emulsion include the following components in parts by weight:

[0144] 100 parts toluene-2,4-diisocyanate (TDI), 160 parts polypropylene glycol-1 (average molecular weight 2000), 50 parts citric acid, 5 parts catalyst, 50 parts triethylamine, 300 parts water;

[0145] The method for preparing the aqueous polyurethane emulsion includes the following steps:

[0146] S1. Mix toluene-2,4-diisocyanate (TDI), polypropylene glycol-1 and catalyst, and heat to 80°C for 4 hours under a nitrogen atmosphere to obtain a prepolymer;

[0147] S2. Citric acid and triethylamine are added to the prepolymer, and the reaction is carried out at 80°C for 3 hours to obtain the intermediate;

[0148] S3. Add water to the intermediate and perform an emulsification reaction by ultrasound to obtain an aqueous polyurethane emulsion.

[0149] The preparation method of the above-mentioned modified alumina coating includes:

[0150] The modified alumina coating is obtained by mixing the components.

[0151] Performance testing

[0152] The performance of the modified alumina coatings in each embodiment and comparative example was tested, as follows:

[0153] 1. Antibacterial performance test:

[0154] The antibacterial properties of the modified alumina coatings in each example and comparative example were tested according to Appendix A of standard HG / T 3950-2007, "Antibacterial Coatings - Test Methods for Antibacterial Performance". Escherichia coli was used as the test bacteria, and the concentration of the bacterial solution used in the test was 5.0 × 10⁻⁶. 5With a CFU / mL concentration and a volume of 0.4 mL, a wooden board was used as the coating test board, and the modified alumina coating of Comparative Example 9 was used as the blank control sample. The antibacterial rate (%) of the modified alumina coatings of each example and the comparative example was recorded.

[0155] The higher the antibacterial rate, the better the antibacterial performance of the modified alumina coating;

[0156] 2. Adhesion test:

[0157] 38g of the modified alumina coatings from each example and comparative example were coated onto a 40mm×40mm×2mm tinplate surface and cured at 60℃ for 9h to obtain test samples. Then, the adhesion of the test samples was tested according to GB / T 9286-2021, and the adhesion grade (level) of the modified alumina coatings from each example and comparative example was recorded.

[0158] The higher the adhesion rating, the worse the adhesion of the modified alumina coating.

[0159] 3. Corrosion resistance test:

[0160] A. Acid corrosion resistance test:

[0161] 38g of the modified alumina coatings from each example and comparative example were coated onto a 40mm×40mm×2mm tinplate surface and cured at 60℃ for 9 hours. An acid corrosion resistance test was conducted according to Method A (immersion method) in GB / T 9274-1988, immersing the test sample in a 10% HCl solution for 80 days. The sample was then removed, dried with filter paper, and visually observed under diffused sunlight. Discoloration and loss of gloss were allowed. The acid corrosion resistance was rated; a higher rating indicates poorer acid corrosion resistance of the modified alumina coating, as detailed below:

[0162] Grade 0 - No abnormalities in the paint film, such as blistering, cracking, peeling, or rusting, are observed on the sample surface;

[0163] Level 1 - The area of ​​abnormal paint film phenomena such as blistering, cracking, peeling, and rust on the sample surface accounts for 0-20% of the total sample surface area, and is not 0;

[0164] Level 2 - The area of ​​abnormal paint film phenomena such as blistering, cracking, peeling, and rust on the sample surface accounts for 20%-40% of the total sample surface area, but not 20%;

[0165] Level 3 - The area of ​​the sample surface with abnormal paint film phenomena such as blistering, cracking, peeling, and rust accounts for 40%-60% of the total sample surface area, but not 40%.

[0166] Level 4 - The area of ​​the sample surface with abnormal paint film phenomena such as blistering, cracking, peeling, and rust accounts for 60%-80% of the total sample surface area, but not 60%.

[0167] Level 5 - The area of ​​the sample surface with abnormal paint film phenomena such as blistering, cracking, peeling, and rust accounts for 80%-100% of the total surface area of ​​the sample, but not 80%.

[0168] B. Alkali corrosion resistance test:

[0169] 38g of the modified alumina coatings from each example and comparative example were coated onto a 40mm×40mm×2mm tinplate surface and cured at 60℃ for 9 hours. An alkali corrosion resistance test was conducted according to Method A (immersion method) in GB / T 9274-1988, immersing the test sample in a 10% KOH solution for 80 days. The sample was then removed, dried with filter paper, and visually observed under diffused sunlight. Discoloration and loss of gloss were allowed. The alkali corrosion resistance was rated; a higher rating indicates poorer alkali corrosion resistance of the modified alumina coating, as detailed below:

[0170] Grade 0 - No abnormalities in the paint film, such as blistering, cracking, peeling, or rusting, are observed on the sample surface;

[0171] Level 1 - The area of ​​abnormal paint film phenomena such as blistering, cracking, peeling, and rust on the sample surface accounts for 0-20% of the total sample surface area, and is not 0;

[0172] Level 2 - The area of ​​abnormal paint film phenomena such as blistering, cracking, peeling, and rust on the sample surface accounts for 20%-40% of the total sample surface area, but not 20%;

[0173] Level 3 - The area of ​​the sample surface with abnormal paint film phenomena such as blistering, cracking, peeling, and rust accounts for 40%-60% of the total sample surface area, but not 40%.

[0174] Level 4 - The area of ​​the sample surface with abnormal paint film phenomena such as blistering, cracking, peeling, and rust accounts for 60%-80% of the total sample surface area, but not 60%.

[0175] Level 5 - The area of ​​the sample surface with abnormal paint film phenomena such as blistering, cracking, peeling, and rust accounts for 80%-100% of the total surface area of ​​the sample, but not 80%.

[0176] The experimental results are shown in the table below:

[0177] Table 7 Performance test results of the modified alumina coatings in each example and comparative example.

[0178]

[0179]

[0180] Figure 1 The figures show actual images of the modified alumina coatings of Example 1 and Comparative Example 1 applied to the flat surface of a tinplate. In the figures, Figure A shows the actual image of the modified alumina coating of Example 1 applied to the flat surface of a tinplate, and Figure B shows the actual image of the modified alumina coating of Comparative Example 1 applied to the flat surface of a tinplate.

[0181] from Figure 1 As shown in Table 7, the modified alumina coating of the present invention has high antibacterial and corrosion-resistant properties.

[0182] Specifically, this invention modifies alumina by controlling the weight ratio of alumina, L-cysteine, and carboxymethyl chitosan. This not only improves the antibacterial properties of alumina but also enhances the compatibility between alumina and waterborne polyurethane emulsions. This allows the modified alumina to be stably and uniformly dispersed in the modified alumina coating, thereby achieving the goal of improving the antibacterial and corrosion-resistant properties of the modified alumina coating.

[0183] In addition, the waterborne polyurethane emulsion synthesized by controlling the amount of toluene-2,4-diisocyanate (TDI), polypropylene glycol and citric acid has good compatibility with modified alumina, which can improve the dispersion and uniformity of modified alumina in modified alumina coatings, and help improve the antibacterial and corrosion-resistant properties of modified alumina coatings.

[0184] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A modified alumina coating, characterized in that, Includes the following components: Modified alumina and waterborne polyurethane emulsion; The method for preparing the modified alumina includes: mixing alumina, L-cysteine ​​and carboxymethyl chitosan to obtain the modified alumina; the weight ratio of the alumina, L-cysteine ​​and carboxymethyl chitosan is 5:(1-5):(1-8). The raw materials of the aqueous polyurethane emulsion include the following components in parts by weight: 100 parts toluene-2,4-diisocyanate, 120-180 parts polypropylene glycol, 15-60 parts citric acid, 0.2-5 parts catalyst, 10-50 parts triethylamine, and 80-300 parts water.

2. The modified alumina coating as described in claim 1, characterized in that, Includes at least one of the following (1)-(6): (1) The weight ratio of alumina, L-cysteine ​​and carboxymethyl chitosan is 5:(2-4):(3-6); (2) The average particle size of the alumina is 30-800 nm; (3) The average molecular weight of the polypropylene glycol is 400-4000; (4) The polypropylene glycol is in the form of 140-160 parts by weight; (5) The citric acid is in the form of 30-50 parts by weight; (6) The weight ratio of the modified alumina and the waterborne polyurethane emulsion is (5-30):

100.

3. The modified alumina coating as described in claim 2, characterized in that, Includes at least one of the following (1)-(3): (1) The average particle size of the alumina is 100-500 nm; (2) The average molecular weight of the polypropylene glycol is 1000-3000; (3) The weight ratio of the modified alumina and the waterborne polyurethane emulsion is (10-20):

100.

4. The modified alumina coating as described in claim 1, characterized in that, Includes at least one of the following (1)-(2): (1) The modified alumina coating also includes additives; (2) The catalyst is at least one of zinc octanoate, dibutyltin dilaurate, and stannous octanoate.

5. The modified alumina coating as described in claim 4, characterized in that, Includes at least one of the following (1)-(2): (1) The additive is at least one of defoamer, wetting agent, leveling agent and filler; (2) The weight ratio of the additive to the waterborne polyurethane emulsion is (0.1-20):

100.

6. The modified alumina coating as described in claim 1, characterized in that, The method for preparing the modified alumina includes: adding alumina, L-cysteine ​​and carboxymethyl chitosan to a solvent, mixing them, and drying them to obtain the modified alumina.

7. The modified alumina coating as described in claim 1, characterized in that, The method for preparing the aqueous polyurethane emulsion includes the following steps: S1. Mix toluene-2,4-diisocyanate, polypropylene glycol and catalyst, and carry out a prepolymerization reaction to obtain a prepolymer; S2. Citric acid and triethylamine are added to the prepolymer to react and obtain the intermediate; S3. Add water to the intermediate to carry out an emulsification reaction, and the waterborne polyurethane emulsion is obtained.

8. The modified alumina coating as described in claim 7, characterized in that, Includes at least one of the following (1)-(2): (1) In step S1, the temperature of the prepolymerization reaction is 70-85℃; (2) In step S2, the temperature of the reaction is 50-80℃.

9. A method for preparing the modified alumina coating according to any one of claims 1-8, characterized in that, include: The modified alumina coating is obtained by mixing the components.

10. The application of the modified alumina coating according to any one of claims 1-8 in antibacterial applications.

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